High frequency antenna



April 1959 J. L. BUTLER 2,881,435

- HIGH FREQUENCY ANTENNA F led Jan. 6, 1954 Jesse L; Butler INVENTOR.

ATTORNEY United States Patent 6 Claims. (Cl. 343-781) This invention relates to directive antenna systems for the radiation and reception of high frequency electio H magnetic energy waves. More particularly, this invention relates to antennas employing a paraboloid reflector to provide directivity of radiation and reception.

In a system employing a paraboloid reflector it 1s essential that a radiator of electromagnetic energy be located at substantially the focal point of the p-araboloicl and direct its energy toward the paraboloid reflector. In conventional practice, electromagnetic energy'is fed through the center of the paraboloid from behind it to the radiating element located at the focal point of the parabola.

It is an object of this invention to provide an improved antenna that is simple in design and economical to produce;

A further object of this invention is to provide an improved antenna useful over a wide range of frequencies; and

A still further object of the invention is to provide an improved antenna capable of efflciently and symmetrically illuminating a parabolic antenna reflector using rear feed.

Other objects of the invention will be apparent from the following description of a typical embodiment thereof, taken in connection with the accompanying drawings.

In accordance with the present invention, there is pro vided a high-frequency antenna. The antenna includes an electrically non-conductive rod forming a dielectric radiator along the surface of which are propagated surface electromagnetic energy Waves and below the surface of which are propagated sub-surface electromagnetic energy waves. A first reflecting means, having a reflective surface adjacent an end of the rod is provided primarily for reflecting the sub-surface waves. A second reflecting means is disposed in the path of the surface waves and has a transverse reflecting surface displaced from the first reflecting surface primarily for reflecting the surface Waves. In this manner the surface and sub-surface waves are radiated in reenforcing phase relation at one of the reflecting surfaces.

In the accompanying drawings:

Fig. l is a three-dimensional view of an antenna embodying this invention; and

Fig. 2 is a cross-sectional view of a portion of the antenna in Fig. 1.

With particular reference to the drawings, an illuminator comprising the dielectric radiator 1 (such as polystyrene rod), reflector 2 and reflector 4 is provided for radiating electromagnetic energy into paraboloid reflector 3. Reflector 4 causes a portion of the energy propagated by dielectric radiator 1 to be reflected in phase with the energy radiated from reflector 2. The arrow 5 points in the direction of result-ant antenna radiation. The dielectric radiator 1 is coupled to cylindrical wave guide 6; a transducer 7 transforms the propagation mode of the energy in rectilinear wave guide 8 to the propagation mode in circular wave guide 6. A mounting bracket 9 supports the illuminator assembly and paraboloid 3. Mounting holes 10 in the bracket permit the assembly of the antenna to a supporting structure.

Dielectric radiators characteristically propagate high frequency electromagnetic energy in two modes: surface waves traveling along the surface of the radiator and sub-surface waves traveling below it. The illuminator for the paraboloid reflector consists of the dielectric radiator 1, surface waves reflector 2 and sub-surface waves reflector 4. The dielectric rod serves as a transmission line terminated in a short circuit by the sub-surface reflector 4, so that the reflected traveling Waves are produced in the dielectric rod. The reflected waves also radiate along the dielectric rod; the distance between the reflector 2 and the short circuit of reflector 4 is so chosen as to cause waves reflected thereby to be in phase with the reflected surface waves.

Energy to be radiated is coupled from a transmitter source through the rectilinear wave guide 8, transducer 7, cylindrical wave guide 6 and dielectric rod 1 to re- I flectors Z and 4, and radiated into paraboloid 3 and thence into space in the direction of the arrow 5. In the preferred embodiment, the dielectric constant has been chosen so that approximately half of the energy is propagated below the surface of dielectric rod 1.

The circular symmetry of the illuminator permits a I nearly perfect symmetrical radiation pattern for illuminating the paraboloid.

Although a circularly symmetrical illuminator is employed in the preferred embodiment, nonsymrnetrical radiation patterns may be obtained by using illuminators of diverse configurations.

The simplicity of the present invention facilitates the economical manufacture of precision units.

While there has been hereinbefore described what is at present considered a preferred embodiment of the in vention, it will be apparent that many and various changes and modifications may be made with respect to the embodiment illustrated without departing from the spirit of the invention. It will be understood, therefore, that all those changes and modifications as fall fairly Within the scope of the present invention, as defined in the appended claims, are to be considered as a .part of the present invention.

What is claimed is:

1. An antenna comprising an electrically nonconductive rod forming a dielectric radiator along the surface of which and through which are propagated electromagnetic energy waves; an electrically conductive tube surrounding a part of said rod adjacent one end thereof and providing a guide for said energy waves; and a reflector adjacent the opposite end of said rod having a conductive surface perpendicular to and surrounding said rod to reflect the surface component of said propagated electromagnetic waves and an electrically conductive tube portion at the center of said perpendicular surface surrounding said opposite end of said rod; and an electrically conductive end cap enclosing said tube adjacent said opposite end of said rod, said tube and said cap providing a reflector primarily for the sub-surface component of said propagated electromagnetic waves, and so positioned relative to said perpendicular surface that said surface and sub-surface components are radiated in phase.

2. An antenna comprising an electrically nonconductive, cylindrical rod forming a dielectric radiator along which are propagated surface electromagnetic energy waves and through which are propagated interior electromagnetic energy waves; an electrically conductive, cylindrical tube surrounding said rod adjacent one end thereof and providing a guide for said energy waves; a surface reflector for said surface waves adjacent the opposite end of said rod having a circular conductive surface attached centrally and perpendicularly thereto to refl'ect primarily said surface waves; and an interior reflector for said interior waves having a cylindrical tube integrally formed with said surface reflector, and surrounding an extension of said rod, the tube beingclosed a't'the end of said extension to reflect primarily said interior waves with said surface and interior waves radiated in phase.

3. An antenna responsive to a source of electroma netic energy comprising an electrically nonconductive cylindrical rod forming a dielectric radiator along which are propagated surface electromagnetic energy waves and through which are propagated interior electromagnetic energy waves; an electrically conductive tube connected to said energy source, surrounding said rod adjacent one end thereof and providing a guide for said energy waves; a surface reflector for said surface waves adjacent the opposite end of said rod having a circular conductive surface attached centrally and perpendicularly to said rod; and an interior reflector for said interior waves having a cylindrical tube integrally formed with said surface reflector, and surrounding an extension of said rod, the tube being closed at the end of said extension, said surface and interior waves being radiated in phase.

4. An antenna system for radiating a beam of electromagnetic energy waves and receptive to electromagnetic energy waves radiated from a source remote from said antenna, comprising an electrically conductive, paraboloid reflecting means to form said beam; an illuminator for said reflector, mounted axially thereto and connected through the center of said paraboloid, comprising an electrically nonconductive rod forming a dielectric radiator along the surface of which and through which are propagated electromagnetic energy waves; an electrically conductive tube surrounding a part of said rod adjacent one end thereof and providing a guide for said energy waves; and, at the opposite end of said rod and substantially at the focal point of said paraboloid, a reflector having a conductive surface perpendicular to and surrounding said rod, and a tube portion at the center of said perpendicular surface surrounding the end of said rod, said tube being closed adjacent said opposite end, the surface and sub-surface components of said waves being radiated in phase.

5. An antenna comprising an electrically nonconductive rod forming a dielectric radiator along the surface of which and through which are propagated electromagnetic energy waves; an electrically conductive tube surrounding apart of said rod adjacentone end thereof and providing a guide for said energy waves at a pre determined propagation mode; a transducer for connecting said guide to a source of electromagnetic energy waves at a different propagation mode; and a reflector adjacent the opposite end of said rod having a conductive surface perpendicular to and surrounding the rod, and a tube portion at the center of said perpendicular surface surrounding the end of said rod, said tube being closed adjacent said opposite end, the surface and subsurface. components of said waves being radiated in phase.

'6. A high frequency antenna, comprising: an electrically nonconductive rod fonning a dielectric radiator along the surface of which are propagated surface electromagnetic energy waves and below the surface of which are propagated sub-surface electromagnetic energy waves; 'a first reflecting means having a reflecting surface adjacent an end of said rod primarily for reflecting said sub-surface waves; and a second reflecting means disposed in the path of said surface waves and having a transverse reflecting surface displaced from the first said .refleeting surface primarily for reflecting said surface waves, whereby said sub-surface and surface waves are radiated in re-enforcing phase relation at one of said reflecting surfaces.

References Cited in the file of this patent UNITED STATES PATENTS Sweden Mar. 17, 1953 

